Insomnia is the disturbance of a normal sleep pattern. For example, when you cannot get to sleep or wake up after only a few hours sleep.

Sleep is a state of consciousnesses, which gives your body time to rest and build up your strength. While you are asleep, your body goes through different stages at approximately 90 minute cycles. These include light sleep, deep sleep and dreaming, also known as rapid eye movement (REM) sleep.

Difficulties with sleep can appear in a variety of ways:

• Difficulty getting to sleep (sleep onset insomnia). This is most common in young people.
• Waking in the night (frequent nocturnal awakening). This is most common in older people.
• Waking early in the morning - the least common type of sleep disturbance.
• Not feeling refreshed after sleep. You may have trouble functioning normally during the day, feel irritable, tired, and find it difficult to concentrate.
• Waking when you have been disturbed from sleep by pain or noise.

Insomnia can last for days, months or even years and can be split into three categories:

• Transient insomnia lasts for 2-3 days.
• Short-term insomnia lasts for more than a few days, but less than three weeks.
• Chronic insomnia can be defined as insomnia most nights for three weeks or longer.

Chronic insomnia can lead to mental health problems such as depression, misuse of alcohol or other medicines in order to gain sleep.

Every individual is different so it is hard to define what normal sleep is for you. Other factors include your age, lifestyle, diet and environment.

Newborn babies can sleep for 16 hours a day, while children of school age need an average of 10 hours.

Adults usually need, on average, seven to nine hours sleep a night. As we get older, it's normal to need less sleep. Most people over 70 need less than six hours sleep per night; and they tend to be light sleepers.